Implantable monitoring probe

ABSTRACT

Disclosed is an ambulatory system for monitoring one or more physiological parameters in a body lumen, such as the esophagus. The system includes an implantable probe having a sensor for the physiological parameter and a transmitter for transmitting data to an external receiver. The probe may be used for monitoring any of various physiological parameters, including pH, temperature, and pressure, within the esophagus or other body lumens. Methods and deployment catheters are also disclosed.

This application is a continuation of U.S. patent application Ser. No.10/687,336, filed Oct. 16, 2013, which is a divisional application ofU.S. application Ser. No. 09/544,373, filed Apr. 6, 2000, which is acontinuation-in-part of U.S. application Ser. No. 09/287,617, filed Apr.7, 1999, all of which being incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to minimally invasive physiologicalmonitoring systems. More particularly, the present invention relates toan implantable probe for monitoring one or more parameters in theesophagus, such as pH, in connection with the detection ofgastroesophageal reflux disease.

Description of the Related Art

Gastroesophageal reflux is a condition in which gastric acid refluxes,or flows in the direction opposite to the normal flow, from the stomachinto the esophagus. Frequent reflux episodes may result in a potentiallysevere problem known as gastroesophageal reflux disease (GERD). GERD isthe most common cause of dyspepsia or heartburn. GERD affectsapproximately 75 million adults in the United States on at least anintermittent basis, and approximately 13 million adults on a dailybasis. As a common cause of chest pain, GERD frequently mimics thesymptoms of a myocardial infarction or severe angina pectoris, which aresigns of severe coronary artery disease. Because their treatments andoutcomes are different, distinguishing between GERD and coronary arterydisease is of paramount diagnostic importance to the patient andphysician.

The lower esophageal sphincter (LES), or valve, is composed of a smoothmuscle ring located at the gastroesophageal junction, and it plays a keyrole in the pathogenesis of GERD. Factors that cause or contribute toGERD include the following: transient relaxation of the LES, delayedstomach emptying, and ineffective esophageal clearance. Another cause ofGERD is decreased resting tone of the LES, which produces incompetence(incomplete closing) of the LES.

At rest, the LES maintains a high pressure, between 10 and 30 mm Hgabove intragastric pressure. Upon deglutition (swallowing), the LESrelaxes before the esophagus contracts, allowing food to pass throughinto the stomach. After food passes into the stomach, the LES contractsto prevent the stomach contents, including gastric acid, from refluxinginto the esophagus. The mechanism of the LES contraction and relaxationis influenced by vagus nerve innervation and hormonal control by gastrinand possibly other gastrointestinal hormones.

Complications of GERD include esophageal erosion, esophageal ulcer, andesophageal stricture. Stricture formation results from scarring of theesophagus following prolonged exposure of the esophageal mucosa to acidreflux. The most common clinical manifestation of stricture is dysphagia(difficulty swallowing). Unlike dysphagia from nonstrictured esophagealreflux, dysphagia caused by stricture is a progressive disorder in thatthe size of a bolus which can pass into the stomach becomesprogressively smaller. Prolonged exposure of esophageal mucosa to acidoften leads to a precancerous condition known as Barrett's esophagus.Barrett's esophagus is characterized by the replacement of the normalsquamous epithelium that lines the esophagus with abnormal columnarepithelium. Barrett's esophagus is clinically important not only as amarker of severe reflux, but also as a precursor to esophageal cancer.

Efforts have been made to define and report as reflux rapid changes ofintraesophageal pH, even while the pH remains within the normalesophageal pH range of 4 to 7. Such pH changes, however, can bedifficult to prove to be caused by true gastroesophageal reflux, and insome instances may not be caused by reflux.

Some have measured gastroesophageal reflux with radioisotope techniques.With these techniques, a radiolabeled meal is fed to the patient. With agamma camera positioned externally on the patient's chest or internallywithin the esophagus, it is possible to detect gastroesophageal refluxcontaining the isotope, regardless of pH. The use of radioactivematerial and the expense of stationary or ambulatory gamma cameras makethe radioisotope method for detection of reflux unattractive.

Intestinal impedance has previously been used as a surrogate formeasurement of gastric emptying into the intestines. In such studies, aliquid or solid meal is administered to a patient, and changes inintestinal impedance are monitored from external electrodes around theabdomen.

The primary and most reliable method of objectively diagnosing GERD,however, is 24-hour measurement of pH within the lower esophagus. Thenormal pH range in the esophagus is between 4 and 7. As a general rule,when gastric acid enters the esophagus from the stomach, theintraesophageal pH drops below 4. An epoch of one second or more duringwhich the intraesophageal pH falls below 4 is considered a reflux event.

Certain methods and apparatus are known in the prior art for 24-hourmonitoring of intraesophageal pH in patients with suspected GERD. Anexample of a system for ambulatory 24-hour recording of gastroesophagealreflux is the Digitrapper™ System (manufactured by Synectics Medical AB,in Stockholm, Sweden) used with glass or Monocrystant™ pH catheters (asdescribed in U.S. Pat. No. 4,119,498) and with the analysis softwareEsopHogram™ (by Gastrosoft, Inc. in Dallas, Tex.). These prior artsystems typically measure pH in the esophageal tract with anintraesophageal catheter and generate reports regarding esophagealexposure of gastric juice.

Currently, ambulatory esophageal pH monitoring is performed by passing apH catheter transnasally into the esophagus, to a point approximately 5cm above the LES. The proximal end of the nasoesophageal catheterextends outside the patient's nose and is usually taped down to thecheek in two places and draped over the ear.

The use of this indwelling nasoesophageal catheter for ambulatory pHmonitoring presents a number of disadvantages. Almost invariably, thecatheter's presence is very uncomfortable to patients, who frequentlydevelop a sore throat and rhinorrhea (runny nose) because of localirritation of oropharyngeal and nasopharyngeal mucous membranes,respectively, from the catheter. In addition, many patients areembarrassed to be seen in public with the catheter assembly attached totheir faces. Furthermore, patients frequently experience an increasedswallowing frequency when the catheter is in place, due to reflexstimulation. This increased swallowing introduces a significant amountof air into the stomach, which can cause abdominal discomfort. Finally,increased swallowing in response to the catheter's presence mayerroneously raise a patient's intraesophageal pH readings because salivais alkaline.

Thus, there remains a need for an ambulatory system that avoids the useof an indwelling nasoesophageal catheter during the assessment ofesophageal pH and other physiological parameters to detectgastroesophageal reflux.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided a monitoring device (sometimes referred to herein as a “probe”)for monitoring at least one physiological parameter at an attachmentsite in a body. The monitoring device comprises a housing, having atissue attachment surface. A pin is movable from a retracted position toallow the tissue attachment surface to be brought into contact with oradjacent tissue at a preselected attachment site, and an extendedposition in which it extends through tissue in contact with or adjacentto the attachment surface. The housing carries at least onephysiological parameter detector.

In accordance with another aspect of the present invention, there isprovided a method of attaching a device to a tissue surface inside of apatient. The method comprises the steps of providing a device having ahousing, a concavity on the housing, a window to permit visualizationthrough the housing of the interior of the concavity, and a pin which isaxially movable between a retracted position and an extended positionwhich extends at least part way across the concavity. The device iscarried on an introduction instrument into the body, and positionedadjacent an attachment site. Tissue is drawn into the concavity, whereit may be visualized through the window. The pin is thereafter advanced(proximally or distally) through the tissue to retain the device at theattachment site.

Preferably, the device further comprises a vacuum lumen in communicationwith the concavity, and the drawing tissue into the concavity stepadditionally comprises the step of applying suction to the lumen. In oneembodiment, the window comprises a transparent wall on the housing, andthe visualizing tissue step comprises observing tissue and the pinthrough the wall of the housing. In one embodiment, the pin comprises amaterial which degrades or absorbs at the attachment site, and themethod further comprises the step of permitting the pin to degradefollowing a sufficient monitoring period of time, thereby releasing thedevice from the tissue surface.

In accordance with a further aspect of the present invention, there isprovided a method of attaching a device to a tissue surface inside of apatient. The method comprises the steps of providing a device having ahousing, a concavity on the housing, and a pin which is axially movablefrom a retracted position within the housing to an extended positionwhich extends at least part way across the concavity. The device iscarried on an introduction instrument into the body, and positioned atan attachment site, such that the concavity is adjacent the tissuesurface at the attachment site. Tissue is drawn into the concavity, andthe pin is advanced through the tissue to retain the device at theattachment site.

In accordance with a further aspect of the present invention, there isprovided a monitoring device for monitoring at least one psychologicalparameter at an attachment site in a body. The device comprises ahousing, having a tissue attachment surface. A pin is movable between aretracted position to allow tissue to be brought into contact with thetissue attachment surface, and an extended position in which the pinextends through the tissue in contact with the attachment surface. Thehousing carries at least one physiological parameter detector. In oneembodiment, the physiological parameter detector comprises a pHdetector.

Preferably, the monitoring device further comprises an RF transmitterfor transmitting data generated by the physiological parameter detector.Alternatively, the monitoring device comprises an electrical contact forcontacting tissue in the body and transmitting data relating to thepsychological parameter through the tissue. In one application, thephysiological parameter is selected from the group consisting of pH,temperature and pressure. Alternatively, the physiological parametercomprises a concentration of a preselected ion on a tissue surface orwithin a body fluid. The ion is preferably selected from the groupconsisting of sodium, potassium, calcium, magnesium, chloride,bicarbonate, and phosphate. In a further aspect of the invention, thephysiological parameter comprises the concentration of a solute within abody fluid, such as glucose, biliruben, creatinene, blood urea nitrogen,urinary nitrogen, renin, and angiotensin.

The monitoring device in one embodiment comprises a microprocessor andnon-volatile memory. The microprocessor controls the various functionsof the monitoring device circuits. The monitoring device sends a digitalsignal that is coded to contain a variety of information. The digitalmessage contains code to uniquely identify the monitoring device. Thisallows multiple devices to be used and inhibits erroneous or straysignal reception. The digital message also indicates what type ofinformation is being sent and a corresponding data packet. The messagealso includes a checksum to help insure that the data transmission wascorrectly sent and received.

The monitoring device provides the ability to power itself off and on.This feature conserves battery power and extends the useful life of themonitoring device. The monitoring device also powers up themicroprocessor and transmitting circuit up separately from the sensorcircuit and alternates the active circuit. This feature furtherminimizes power consumption and further extends the useful life of thepower supply.

Further features and advantages of the present invention will becomeapparent to those of ordinary skill in the art in view of the detaileddescription of preferred embodiments, which follows, when consideredtogether with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a person with the physiologicalparameter monitor in place within the esophagus.

FIG. 2 is a schematic view of one embodiment of an electrical circuitfor the physiological parameter monitor.

FIG. 3 is a schematic view of a preferred embodiment of thephysiological parameter monitor circuit, wherein the circuit alsoincludes a microprocessor.

FIG. 4 is a schematic side view of one embodiment of a physiologicalparameter monitor.

FIG. 5 is a schematic side view of the physiological parameter monitorwith an elastic band attached.

FIG. 6 is a cut-away side view of the esophagus with endoscopicplacement of the monitor by means of an elastic band.

FIG. 7 is a side elevational cross section through an implantable probein accordance with the present invention, removably attached to adeployment device.

FIG. 8 is a schematic representation of an endoscope having a deploymentdevice and a probe positioned within the esophagus.

FIG. 9 is a schematic illustration as in FIG. 8, with tissue drawn intothe tissue cavity.

FIG. 10 is a schematic representation as in FIG. 9 with an attachmentpin advanced through the tissue.

FIG. 11 is a schematic representation as in FIG. 10, with the deploymentdevice detached from the probe.

FIG. 12 is a side elevational view of an alternate deployment device inaccordance with the present invention.

FIG. 13 is a side elevational partial cross section through the distalend of a deployment catheter of the type illustrated in FIG. 12,removably connected to a probe.

FIG. 14 is a side elevational view as in FIG. 13, with the probeattached to the tissue and the deployment catheter disconnected from theprobe.

FIG. 15 is a side elevational view of a further embodiment of adeployment device in accordance with the present invention.

FIG. 16 is an enlarged cross-sectional view through the distal end ofthe deployment device of FIG. 15, following application of vacuum.

FIG. 17 is a side elevational view as in FIG. 16, following distaladvancement of a needle.

FIG. 18 is a side elevational view as in FIG. 17, following distaladvancement of a dowel or pin through the needle.

FIG. 19 is a side elevational view as in FIG. 18, following proximalretraction of the needle.

FIG. 20 is a side elevational view as in FIG. 19, following detachmentof the docking structure from the probe.

FIG. 21 is a side elevational view as in FIG. 18, showing a transnasalembodiment of the invention.

FIG. 21A is a schematic cross section through a probe, followingattachment to a tissue surface.

FIG. 22A is a side elevational view of an additional embodiment of adeployment device in accordance with the present invention.

FIG. 22B is an enlarged cross sectional view through the distal end ofthe deployment device of FIG. 22A, positioned adjacent a tissue surface.

FIG. 22C is a side elevational view as in FIG. 22B, followingapplication of vacuum to the tissue.

FIG. 22D it a side elevational view as in FIG. 22C, following deploymentof the pin.

FIG. 22E is a side elevational view as in FIG. 22D, following retractionof the locking wire and deployment of the probe from the deliverydevice.

FIG. 23 is a circuit diagram of a preferred embodiment of thephysiological parameter monitor circuit, wherein the circuit includes amicroprocessor and an ISFET sensor.

FIG. 24 is a circuit diagram of an alternative embodiment of thephysiological parameter monitor circuit, wherein the circuit includes amicroprocessor and an antimony sensor.

FIG. 25 is a flow chart showing the main functions of the monitormicroprocessor.

FIG. 26 shows the message structure of the digital messages sent by themonitor to a waiting receiver.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a method and system for monitoringphysiological parameters within a body lumen (cavity). The inventionalso comprises methods for attaching a physiological parameter monitorto a wall of a body lumen. The term “lumen” as used herein refers to thespace within a tubular wall (e.g., a vessel) or the cavity within ahollow organ. While the invention is described in detail as applied tothe human esophagus, those skilled in the art will appreciate that itcan apply to other body lumens or cavities, such as those of thestomach, colon, rectum, bladder, uterus, vagina, biliary ducts(including the common bile duct), or blood vessels. The term “esophagus”in this discussion includes the lower esophageal sphincter (LES). Wheredifferent embodiments have like elements, like reference numbers areused.

FIG. 1 illustrates how physiological parameter data can be relayed bythe monitor 18, which is positioned within the esophagus 30, to aradiofrequency receiver 32 (hereinafter “radioreceiver”) located outsidethe body of a person 40. As is illustrated in FIG. 1, more than onemonitor 18 can be implanted so that data can be obtained from aplurality of different locations as will be described in greater detailbelow.

In certain embodiments, this transmission of data is accomplished viaradio telemetry in real time. The radioreceiver 32 receivesphysiological parameter data within 12 seconds after it is measured bythe monitor 18. After reception of this data, the radioreceiver 32apparatus can record, manipulate, interpret and/or display the data,using technology well known to those skilled in the art. In certainembodiments, the patient can wear the receiver 32 and recorder on, forexample, a belt, bracelet, arm or leg band, or necklace during theperiod of pH study or other analysis.

The receiver 32 and recording apparatus can have buttons or otherswitches thereon that enable the patient or other person to mark certainevents in time during the recording period, such as when symptoms occur,when the patient is eating, when the patient is recumbent (either supineor prone), or when the patient is about to sleep. This event marking canbe made in any recording medium that is used for recording thephysiological parameter, such as magnetic tape or an electronic digitalmemory chip, in ways that are well known to those of skill in the art.

The monitor 18 can be made to sense the position of the patient, whetherhorizontal, vertical, or somewhere between horizontal and vertical. Suchposition sensing can be accomplished through the use of electricalswitches that utilize floating fluid bubbles, as used in mechanicallevel sensing, or electronic gyroscopic techniques as are known to thoseskilled in the art.

In certain embodiments, the monitor 18 can record and compressphysiological parameter data as it is gathered, rather than transmit thedata in real time. Following the assessment period, or at intervalstherein, an external transceiver can be used to download pulses ofcondensed data. Transmission of data can be initiated at predeterminedintervals or by an activation signal sent from the external transceiveror other activating device to the monitor 18, as will be understood bythose of skill in the art. In this manner, a tabletop transceiver can beutilized, either at the patient's home, or in the physician's office orother clinical site.

In other embodiments, the monitor 18 can record, compress, and storephysiological parameter data as it is gathered, using a memory chip andmicroprocessor. The person 40 can excrete the monitor 18 in his or herstool, and the monitor 18 can be retrieved. Subsequently, data stored inthe monitor 18 can be downloaded into an external data retrieval device,which can be a computer or other analysis machine located outside thepatient's body. This downloading can be accomplished by IR or RFtransmission in response to an activation signal, using magnetic fieldor radiofrequency technology well known to those skilled in the art.

Although the typical gastroesophageal reflux study lasts 24 hours, othertime periods for this study can exist, such as, 48 hours or longer.Through the use of this invention, it is possible that fewer than 24hours may be needed to establish the diagnosis of GERD, particularlybecause real-time monitoring can provide nearly immediate evidence ofreflux events. The actual durations of various reflux studies using thepresent invention will be apparent to those of skill in the art.

FIG. 2 illustrates a simplified circuit for a monitor 18 of aphysiological parameter (hereinafter “monitor 18”). This monitor 18 mayalso be referred to as a “probe” or “pill”. In the particular embodimentillustrated in FIG. 2, pH is the physiological parameter to be sensed,and it is detected by a transducer 110, which comprises a pH sensor andpreferably also a reference sensor. In the present invention, amonitoring transducer (hereinafter “transducer”) can be any transducerthat senses a physiological parameter and furnishes a signal one ofwhose electrical characteristics, such as current or voltage, isproportional to the measured physiological parameter.

Although a pH sensor is described here, those skilled in the art willappreciate that a sensor of any of a variety of other physiologicalparameters, such as pressure or temperature, can be detected andmonitored. Sometimes, temperature and/or pressure will be sensed andtransduced together with pH, in order to adjust the pH readings and makethem more accurate, or to supply additional data helpful in the analysisof the patient's condition. In addition, the concentration of ions orother solutes present in body fluids can be detected and analyzed usingthis invention. For example, ions such as sodium, potassium, calcium,magnesium, chloride, bicarbonate, or phosphate may be measured. Othersolutes whose concentrations in body fluids are of importance and may bemeasured by the present invention include, among others, glucose,bilirubin (total, conjugated, or unconjugated), creatinine, blood ureanitrogen, urinary nitrogen, renin, and angiotensin. Any combination oftwo or more of the preceding parameters may be sensed by the transducer110. For any physiological parameter sensed and transduced by means of atransducer, a reference sensor may or may not be required.

FIG. 2 also illustrates a radiofrequency transmitter circuit 112 and apower source 114. The radiofrequency transmitter circuit 112 cancomprise an antenna (or antenna coil), and the antenna can be at leastin part external to the monitor shell 120 (seen in FIG. 4).Alternatively, the antenna, if present, can be entirely self-containedwithin the monitor shell 120. As an alternative to RF transmission, asignal which is indicative of the monitored parameter can be propagatedthrough the patient's tissue from an electrical contact on the probe toa conductive dermal electrode or other conductor in contact with thepatient.

When located within the monitor 18, the power source 114 can be abattery or capacitor or any other device that is capable of storing anelectrical charge at least temporarily. In a battery powered embodiment,battery life can be extended by disconnecting the battery from othercircuit components thereby limiting parasitic current drain. This can beaccomplished in a variety of ways, such as by including a magneticallyactivated switch in the monitor 18. This switch can be used to connector disconnect the battery as needed. By packaging the monitor 18 with anadjacent permanent magnet, the switch can be opened therebydisconnecting the battery and the shelf life of the device can thus beextended. Removing the monitor 18 from the packaging (and the adjacentpermanent magnet) closes the switch and causes the battery to becomeconnected and supply power to the monitor 18.

In alternative embodiments, the source of power to the monitor 18 can beexternal to the monitor 18 itself. For example, the monitor 18 canderive power from an external electromagnetic radiofrequency (RF)source, as occurs with passive RF telemetry techniques, such as RFcoupling, that are well known to those skilled in the art. The monitor18 can be energized by a time-varying RF wave that is transmitted by anexternal transceiver 32, also known as an “interrogator,” which can alsoserve as a reader of data from the monitor 18. When the RF field passesthrough an antenna coil located within the monitor 18, an AC voltage isinduced across the coil. This voltage is rectified to supply power tothe monitor 18. The physiological parameter data stored in the monitor18 is transmitted back to the interrogator 32 (FIG. 1), in a processoften referred to as “backscattering.” By detecting the backscatteringsignal, the data stored in the monitor 18 can be fully transferred.

Other possible sources of power for the monitor 18 include light, bodyheat, and the potential difference in voltage that can be generated inbody fluids and detected by electrodes made of varying materials. Theharnessing of such power sources for biotelemetry purposes is welldescribed in R. Stuart Mackay: Bio-Medical Telemetry, Sensing andTransmitting Biological Information from Animals and Man, 2d ed., IEEEPress, New York, 1993, whose section entitled “Electronics: PowerSources” is hereby incorporated herein by reference.

FIG. 3 illustrates alternative embodiments of the physiologicalparameter monitor circuitry. In this embodiment, a microprocessor 116,also called a central processing unit (CPU), is illustrated. Thismicroprocessor 116 can perform one or more functions, includingtemporary storage or memory of data, reception of input signal from thetransducer, and transformation between analog and digital signals, amongother functions that will be apparent to those skilled in the art. Thetransducer 110, radiofrequency transmitter 112, and power supply 114 arealso present. Many other circuitry components that can help to generate,amplify, modify, or clarify the electrical signal can be used in otherembodiments of the monitor. Such components include buffers, amplifiers,signal offset controls, signal gain controls, low pass filters, outputvoltage clamps, and analog-to-digital converters, among others. Numerouspossible circuitry features of a portable pH monitoring device, all ofwhich can be used in the present invention, are well described in U.S.Pat. No. 4,748,562 by Miller, et al., the disclosure of which isincorporated in its entirety herein by reference.

In certain embodiments, the monitor 18 further comprises a digitalrecorder or memory chip (not illustrated), which records the transducedphysiological parameter data. This recorder or memory chip will allowtemporary storage of this data accumulated over time (e.g., over aperiod of 24 hours for a typical gastroesophageal reflux study).

FIG. 4 schematically illustrates the configuration of certainembodiments of the physiological monitor 18. In this embodiment, anouter shell 120 surrounds the monitor's 18 electronic components. Thetransducer 110, the radiofrequency transmitter 112, the power supply114, and a microprocessor 116 are encased within the outer shell 120. Incertain embodiments, the shape of the shell 120 can resemble that of apill or gel capsule, as commonly used in various oral drug deliverysystems.

The shell 120 can be made of any of various materials, includingplastics such as polycarbonates, polyethylene, polytetrafluoroethelyne(Teflon®), nylon, delrin, or polyethylene terephthalate. The materialused for the shell 120 should be resistant to water and acidicenvironments because the shell will be exposed, in some embodiments, tofood, water, and gastrointestinal contents, including gastric acid,which is very caustic (with a pH of approximately 1).

The shell 120 can have a lubricious coating applied to its outersurface, which reduces friction between the shell 120 and any object ormaterial that comes in contact with the shell 120, such as theesophageal wall or any food or fluids that flow down the esophagus 30past the monitor. Such a coating can be made of silicone, siliconederivatives, or other hydrophilic materials that will be apparent tothose skilled in the art. This slippery coating on the surface of theshell 120 will reduce the likelihood of occurrence of the followingevents: (1) ingested material will adhere to the monitor 18, (2) theesophagus 30 will become irritated from repeated contact with themonitor 18 during peristalsis of the esophagus 30, and (3) peristalsisor flowing food or fluid will cause detachment of the monitor 18 fromits attachment site.

In certain embodiments, the shape of the shell 120 is streamlined withsmooth rounded corners. This feature helps to avoid injury to thegastrointestinal mucosa during endoscopic placement of the monitor 18,while the monitor 18 is attached to the esophagus, and, when the monitor18 becomes unattached from the esophageal wall, while the monitor 18passes through the gastrointestinal tract and is excreted in the stool.Preferably, detachment occurs from about 2 days to about 10 daysfollowing attachment to the esophageal wall.

The physiological monitor 18 can be placed in the esophagus 30 in avariety of ways. In certain embodiments of the present method, themonitor 18 is placed into the esophagus 30 through the use of a flexibleor rigid endoscope 160 inserted through the nose or mouth of the person40. The monitor 18 can be constrained within or by a deployment device,such as a catheter, until the physician visually verifies attachmentthrough the endoscope 160. Then the monitor 18 can be intentionallydeployed and left within the esophagus, using methods known to those ofskill in the art.

In other embodiments, a physician can attach the monitor 18 directly tothe inner aspect of the esophageal wall through an opening in theesophagus 30 (esophagotomy) or stomach 36 (gastrotomy).

The physiological monitor 18 can be attached to the esophagus 30 in avariety of ways, also referred to herein as “attachment means.” Incertain embodiments, as shown in FIG. 4, the monitor shell 120 has aneyelet attachment 122, which serves to hold a suture 30, string, staple,or other securing structure, which can secure the monitor to the wall ofthe esophagus or other body lumen wall. Besides the eyelet attachment122, many other possible modifications of or attachments to the shell120, such as one or more loops, rings, brackets, tacks, hooks, clips,strings, threads, or screws, can be utilized to facilitate theattachment or fixation of the monitor to a lumenal wall.

The monitor 18 can, in some embodiments, be attached to the esophagus 30through the use of a clip, which may resemble, for example, an alligatorclip. This clip may or may not utilize a spring mechanism, and it canhold the monitor in place by capturing, or “pinching,” the mucosa andsubmucosa of the esophagus 30 between its arms or “jaws.” The clip canhave one or more of its parts made of one or more absorbable ordissolvable materials, such as are described below and are known tothose skilled in the art. This dissolvable material can facilitate theremoval of the monitor 18 from the wall of the esophagus 30 after agiven period of time. As materials in the clip dissolve, the tension inthe clip that causes it to hold onto, or pinch, the esophagus 30 willeventually decrease, and the clip will break free of the esophagus 30and travel through the gastrointestinal tract and into the patient'sstool.

In certain embodiments of the present method, as shown in FIG. 5, themonitor 18 is attached to the esophagus 30 by means of a suture loop oran elastic band 150. The elastic band can be attached to the monitor 18with an absorbable or nonabsorbable suture, string, or thread, otherwisereferred to as a “tether” 152. This tether 152 can be made from avariety of materials, such as a polymeric filament, which can beabsorbable or nonabsorbable in vivo.

In some embodiments, the tether 152 can be attached to a tooth, such asa molar, of a person. The monitor 18 is thus suspended in the esophagusby the tether 152, which is attached at its other end to the tooth. Theattachment to the tooth can be performed by means of an elastic band,plastic band, adhesive materials, or any other means for attaching astructure to a tooth, as are well known in the dental art.

As shown in FIG. 6, the elastic band 150 can be placed around aprotuberance 154 in the wall of the esophagus 30 or other body lumen.Such a protuberance 154 can be found as a naturally occurringpathological structure, such as a polyp, or it can be formed by aphysician (as a “quasi-polyp”) using an endoscope 160 by applyingsuction to the wall of the esophagus 30. Such suction-inducedprotuberances 154 in the esophagus 30 are well known to those skilled inthe art and represent a commonly used method of ligating (tying off)esophageal varices, which are enlarged blood vessels in the wall of theesophagus 30 caused by elevated portal venous pressure.

Although endoscopic ligation techniques typically result in necrosis ofthe tissue that is elevated into a protuberance 154 and ligated, in thepresent method the aim of this technique is merely to provide astructure in the lumen of the esophagus 30 or other body lumen uponwhich to attach temporarily the physiological parameter monitor 18.Thus, it may be desirable not to attach the elastic band 150 to theprotuberance 154 too tightly, so as to avoid compromise to the bloodsupply to the protuberance 154.

In order to avoid exposure of the attachment site to refluxed gastricacid, it will at times be desirable to attach the monitor 18 to theesophagus 30 at a site some significant distance rostral (cephalad) tothe LES. The monitor 18 can thereby be suspended from the esophagealattachment site by the tether 152, such that the monitor 18 ispositioned close (typically 5 cm superior) to the LES, to facilitatedetection of gastroesophageal reflux. This technique optimizes thelikelihood that while the monitor 18 is exposed to refluxed gastricacid, the esophageal attachment site is not so exposed because it issufficiently far from the LES as to avoid the surge of refluxed gastriccontents. Distances between the attachment site and the monitor 18 of atleast about 0.5 cm, and as much as 10 cm or more, may be utilized forthis purpose.

In other embodiments of the present method, the monitor 18 can beattached to the wall of the esophagus 30 or other body lumen using anadhesive substance (hereinafter “adhesive”) either alone or incombination with the mechanical attachment structures disclosed herein.This adhesive can be any of a variety of cyanoacrylates, derivatives ofcyanoacrylates, or any other adhesive compound with acceptable toxicityto human esophageal cells that provides the necessary adhesionproperties required to secure the monitor 18 to the wall of theesophagus 30 for at least a sufficient monitoring period of time. Incertain embodiments the monitor 18 can be directly attached to the wallof the esophagus 30 with the adhesive. In other embodiments, the monitor18 can be attached indirectly, utilizing an intermediate structure, suchas an anchor, to which the monitor 18 attaches and which is in turnadhered to the esophagus 30 by means of the adhesive. One example ofthis type of intermediate structure is an elongate strip of cloth orplastic, secured at one end to the shell 120 and having a tissueattachment surface along its length or at the other end for enhancingadhesive or mechanical bonding to the esophagus 30. Other intermediatestructures and materials can be used, as will be apparent to thoseskilled in the art.

In other embodiments of the present method, the monitor 18 is attachedto the esophagus 30 using a self-expandable support structure (notillustrated) that expands or widens to span the diameter of the bodylumen, so as to retain the monitor 18 therein. Suitable supportstructures include self-expandable wire cages, such as are used forsupporting grafts in the abdominal aorta and elsewhere in the vascularsystem. Stents, struts, and other structural devices known to those ofskill in the art may be used. Many of these structural devices are usedin the fields of vascular radiology and cardiology for the purpose ofmaintaining patency in blood vessels. These support structures can bemade from a variety of materials such as stainless steel, nitinol, orpolymeric filament, which can be absorbable or nonabsorbable in vivo.

In further embodiments of the present method, the monitor 18 is attachedto the esophagus 30 using one or more sutures, clips, staples, tacks,pins, hooks, barbs, or other securing structures that can at leastpartially penetrate the mucosa of the esophagus. These securingstructures can be made from a variety of materials, including absorbablematerials, such as polylactic acid (PLA) or copolymers of PLA andglycolic acid, or polymers of p-dioxanone and 1,4-dioxepan-2-one. Avariety of absorbable polyesters of hydroxycarboxylic acids may be used,such as polylactide, polyglycolide, and copolymers of lactide andglycolide, as described in U.S. Pat. Nos. 3,636,956 and 3,297,033, whichare hereby incorporated in their entirety herein by reference. The useof absorbable materials allows the securing structure to dissolve orresorb into human tissue after a known or establishable time range, suchas 48 to 72hours, and the monitor 18 can thereby become detached fromthe esophagus 30 and can then be excreted in the patient's stool.

For example, one or more short pointed barbs can be integrally formedwith the shell 120 or secured thereto using any of a variety ofattachment techniques which are suitable depending upon the compositionof the shell 120 and the barb. This embodiment can be pressed into thewall of the esophagus, thereby causing the barb or barbs to penetratethe mucosa and enter the submucosa. Preferably, any such barbs will notpenetrate the muscular wall surrounding the submucosa. Hooks may also beattached to or integrally formed with the shell 120, so that the shell120 can be hooked onto the wall of the esophagus, possibly incombination with the use of a bioadhesive. Such hooks and barbs may beformed from a bioabsorbable or dissolvable material as has beendiscussed, to permit detachment of the monitor after a suitable periodof time.

In accordance with a further aspect of the present invention, themonitoring device may be provided with a tissue attachment surfaceadapted for contacting a tissue site. A pin is movable from a retractedposition to allow the tissue attachment surface to be brought intocontact with or closely adjacent the tissue at the preselectedattachment site, and an extended position in which it extends throughthe tissue adjacent the attachment surface. One embodiment having aconcavity at the tissue attachment site is illustrated in FIG. 7.

As illustrated in FIG. 7, the monitor or probe 18 is provided with anouter shell 120, for enclosing a transducer 110, such as a pH sensor orother detector as has been described herein. The transducer 110 may berecessed within the shell 120 and exposed to the external environmentthrough a fluid port 111. Alternatively, the transducer 110 may bemounted in the wall of the shell 120, or positioned on the exteriorsurface of the shell 120, depending upon the nature of the transducer110 and its fluid contact and surface area requirements. The transducer110 is in electrical communication with the electronics of the probe 18,such as a transmitter 112, CPU 116 and batteries or other power supply114 as has been discussed.

The shell 120 is provided with a tissue attachment cavity 124 forreceiving tissue at the attachment site. The shell 120 is furtherprovided with a docking structure 126, such as a threaded aperture 128or other structure for removable connection to a delivery catheter 138.Preferably, the docking structure 126 is in communication with theattachment cavity 124 such as by a vacuum port or other lumen 130. Thisenables application of a vacuum through the delivery catheter 138 andinto the cavity 124, to draw tissue into the cavity 124 as will bediscussed below.

The delivery catheter 138 is provided with a proximal end (notillustrated) and a distal end 140. The distal end 140 is provided with adocking structure 142 such as a complimentary thread 144 for removablyengaging the threaded aperture 128 on docking structure 126. Any of avariety of alternative releasable docking structures may be utilized, aswill be apparent to those of skill in the art in view of the disclosureherein.

The delivery catheter 138 is further provided with a central lumen 146having an axially movable plunger 148. Plunger 148 is provided with adistal end 162 having a removable attachment pin 164 carried thereon.

In use, the probe 18 is removably carried by the delivery catheter 138,and may be advanced through the working channel on an endoscope or otheraccess device to an attachment site. Alternatively, the deliverycatheter is positioned at the attachment site without the use of ascope. Deployment can be accomplished “blind”, using indicia other thanvisualization. For example, by monitoring psi in a suction (e.g. 15-25mm

Hg) applied to the cavity 124, the presence of tissue at the suctionaperture in the cavity 124 can be observed.

The probe 18 is positioned such that the attachment cavity 124 isadjacent the attachment site. A vacuum is applied through the lumen 146,to draw mucosa or other tissue into the attachment cavity 124. Once asufficient volume of tissue has been drawn into the attachment cavity124, the plunger 148 is advanced distally to drive the pin 164 throughthe tissue to pin the probe 18 to the attachment site. In theillustrated embodiment, a pin guide 132, such as a blind lumen, isprovided on the distal end of a pin travel path, to further secure theprobe 18 at the tissue site. Following deployment of the pin 164, thepin is detached from the distal end 162 of plunger 148, and the deliverycatheter 138 is detached from the docking structure 126 on probe 18.

Preferably, the shell 120 is provided with at least a window zone orviewing area 166 to permit endoscopic visualization of the attachmentcavity 124. This enables the clinician to view the tissue drawn into theattachment cavity 124, and visually assess the point at which asufficient amount of tissue has been drawn into attachment cavity 124 toprovide an adequate engagement between the pin 164 and the tissue tosecure the probe 18 to the attachment site. Window 166 may be a separatestructure, such as a plastic or glass wall which is transparent tovisible light. Alternatively, the entire shell 120 may be constructedfrom a relatively clear material, such as polycarbonate, polysulfone ora thermoset material such epoxy, so that the attachment cavity 124 maybe viewed through the opposing side of the shell 120.

The pin 164 may comprise any of a variety of materials such asabsorbable or degradable materials discussed above, which will permitthe probe 18 to automatically disengage from the attachment site after aperiod of time. Alternatively, the pin 164 may comprise any of a varietyof biocompatible structural materials which are well known in themedical art, such as stainless steel, titanium, high densitypolyethylenes, nylon, PTFE, or others which are well known in the art.

One method of attaching the probe to the tissue surface is furtherillustrated by FIGS. 8-11. As illustrated in FIG. 8, the probe 18 isattached to a deployment catheter 138, which extends through the workingchannel of an endoscope. The endoscope carrying the deployment catheter138 and probe 18 is transluminally advanced through the esophagus orother body lumen or hollow organ to position the probe 18 at theattachment site. Once positioned at the site, vacuum is applied to theprobe to draw mucosa into the chamber. In the illustrated embodiment,the wall of the probe is clear and a viewing zone 166 is provided with aconvex curved outer surface to magnify the image of the mucosa withinthe attachment cavity 124. Alternatively a flat wall may be used.

Depending upon the desired attachment site and other clinicalrequirements, the deployment assembly may further be provided with oneor more steering structures to advance the probe laterally within thelumen, in order to position the attachment cavity 124 sufficientlyclosed to the mucosal layer to draw mucosa into the attachment cavity124. For example, the delivery catheter 138 and/or endoscope may beprovided with an inflatable balloon on a medial side, which, uponinflation, will advance the probe laterally such that the attachmentcavity 124 is firmly positioned against the lateral wall. Axiallymovable deflection wires and other steering structures are well known inthe catheter and endoscope arts, and can be readily incorporated intothe delivery catheter 138 as desired. The catheter may also be providedwith torque transmission enhancement structures, such as a braided orwoven polymeric or metal wall layer.

Referring to FIG. 10, the endoscope is utilized to visualize the mucosawithin the attachment cavity 124 following application of vacuum.Preferably, sufficient vacuum is applied to cause the mucosa to contact(“wet”) the top of the cavity, before the pin is advanced through thetissue. Following deployment of the pin, the deployment catheter isdisengage from the probe and removed.

An alternate delivery catheter is illustrated in FIGS. 12-14. Referringto FIG. 12, the delivery catheter 138 is provided with a dockingstructure 126 such as a collet 168. Collet 168 comprises two or three ormore arms 170 which are movable between a generally axial orientationfor grasping the probe and an inclined orientation for releasing theprobe. Each arm 170 is provided with a distal attachment surface 172,such as on a proximal face of a radially inwardly directed flange. Thearms 170 may be biased radially outwardly from the longitudinal axis ofthe delivery catheter 138, or may be mechanically linked to a proximalcontrol for opening the collet 168 to release the probe.

The collet 168 is attached to the distal end of a tubular body 174. Theproximal end 176 of tubular body 174 is provided with a manifold 178,having a vacuum port 180 and a plunger 182 thereon. Vacuum port 180 isin communication with a central lumen extending through tubular body 174as has been described, for applying a vacuum to the attachment cavity124 in probe 18. The plunger 182 is axially movable to deploy a tissuepin 164 through mucosa or other tissue drawn into the attachment cavity124.

A proximal control 186 may be manipulated to axially proximally retractthe movable sleeve 184, to open and close the collet 168. Referring toFIG. 13, the delivery catheter 138 is illustrated with the movablesleeve 184 in a distal position, to lock the collet 168 to the dockingstructure 126 on probe 18. The proximal projection 188 is provided withone or more radially outwardly extending projections, such as an annularflange 190, for engaging the attachment surfaces 172 on the collet 168.

In this embodiment, the docicing structure 126 comprises a proximalprojection 188 illustrated as a cylindrical element having a centrallumen extending therethrough for both axially movably receiving the pin164 and providing communication between the central lumen and theattachment cavity 124. Multiple lumen systems may also be devised, inwhich the pin travels through a different lumen than the vacuum, as willbe apparent to those of skill in the art in view of the disclosureherein.

Following deployment of the pin 164, as has been previously discussed,the proximal control 186 is manipulated to proximally retract the sleeve184, thereby opening collet 168 to release the docking structure 126.

Any of a variety of docking structures can be readily devised, as willbe apparent to those of skill in the art in view of the disclosureherein. In general, the docking structure permits a removable attachmentof the probe to a deployment catheter. The docking structure permitscommunication between a vacuum lumen in the deployment catheter and avacuum pathway in the probe. In addition, the docking structure permitscommunication between a deployment element in the catheter and a pinadapted to cross at least a portion of the cavity.

The attachment cavity 124 in any of the foregoing probe embodiments canhave any of a variety of configurations. Preferably, the depth measuredin the radial direction is related to the cross-sectional area of theopening of the cavity in a manner that permits mucosa or other tissue toprolapse into the cavity to a sufficient depth to accomplish the pinfunction without causing unnecessary trauma to the tissue. In general,depth to opening ratios on the order of about 1:1 are presentlycontemplated. In general, the tissue opening to the cavity 124 will havean axial length within the range of from about 3 mm to about 5 mm, awidth of from about 3 mm to about 5 mm and a depth of from about 3 mm toabout 5 mm.

Preferably, the vacuum port or ports between the vacuum lumen and theattachment cavity 124 are positioned sufficiently far away from theopening of the cavity that a sufficient volume of tissue will be drawninto the cavity 124 before occluding the vacuum ports. Two or more portsmay be provided, to allow additional application of vacuum followingocclusion of the first vacuum port.

Preferably, the opposing surface of the cavity towards which the pin isadvanced is provided with a texture or other friction enhancingstructure, for assisting to stabilize the tissue during the pindeployment step. Friction enhancing surfaces, such as a plurality ofridges or grooves may be utilized, to assist in retaining tissue whileat the same time minimizing trauma.

Referring to FIG. 15, there is illustrated a side elevational view of analternate delivery catheter 138 in accordance with the presentinvention. The delivery catheter 138 comprises a tubular body 202 havinga proximal end 200 and a distal end 140. The delivery catheter 138 hasan overall length within a range of from about 60 cm to about 80 cm, anda maximum outside diameter through the tubular body 202 of preferably nomore than about 3 mm. Construction materials and manufacturing methodsfor the tubular body 202 as well as components of the delivery systemare well understood in the catheter manufacturing arts.

The tubular body 202 comprises an outer sleeve 204 which extends fromproximal end 206 to a distal end 208. The distal end 208 of outer sleeve204 is connected to or integrally formed with a docking structure 142,which will be discussed in greater detail below. The proximal end 206 isspaced sufficiently far (proximally) from the docking structure 142 thatthe proximal end 206 remains outside of the patient during the procedurewhile the docking structure 142 is at the treatment site. In general,the length of the outer sleeve 204 is from about 30 cm to about 60 cm,and the length of the docking structure 142 is within the range of fromabout 2 cm to about 10 cm.

An intermediate tube 210 extends axially through the central lumen inouter sleeve 204. Intermediate tube 210 is movably positioned within theouter sleeve 204 such that it can be moved between a first position inwhich a distal end 214 of intermediate tube 210 removably engages theprobe 18, and a second position in which the distal end 214 ofintermediate tube 210 is disengaged from the probe 18. A releasableshaft lock 211 is preferably provided to allow the position of theintermediate tube 210 to be locked with respect to the outer sleeve 204,such as to secure the probe 18 within the docking structure 142 duringplacement. Preferably, the intermediate tube 210 is axially reciprocallymovable within the outer sleeve 204 between the first and secondpositions.

Intermediate tube 210 extends from a manifold 212 to the distal end 214.Manifold 212 may be provided with any of a variety of access ports,depending upon the desired functionality of the delivery catheter 138.In the illustrated embodiment, the manifold 212 is provided with avacuum port 215. The vacuum port 215 is in communication with a centrallumen (not illustrated) within the intermediate tube 210, whichcommunicates with the cavity 124 in probe 18 when the probe is engagedin the docking structure 142. This enables application of vacuum to thevacuum port 215, to draw tissue within cavity 124 in the probe 18 as hasbeen discussed.

Manifold 212 is also preferably provided with an access port which maybe provided with a Tuohy Borst valve 216, for axially movably receivinga needle tubing 218. Needle tubing 218 extends throughout the length ofthe intermediate tube 210, and is advanceable into the cavity 124 aswill be discussed.

A pin plunger 148 is axially movably positioned within a central lumenin the needle tubing 218. Pin plunger 148 extends from a proximal end220 which remains outside of the proximal end of the needle tubing 218,to a distal end which is positioned at or about a distal end 214 of theintermediate tube for reasons which will become apparent. The proximalend of pin plunger 148 may be connected to any of a variety of controls,such as a lever or slider switch.

In one embodiment of the invention, the outer sleeve 204 comprisesTeflon, having an axial length of about 60 cm. The intermediate tube 210comprises nylon, having an axial length of about 80 cm. Both the outersleeve 204 and intermediate tube 210 may be extruded from any of avariety of materials well known in the catheter arts.

The manifold 212 is preferably injection molded, in accordance with wellknown techniques. Needle tubing 218 may comprise stainless steel orvarious polymers such as PET, having an outside diameter of about 0.040inches, an inside diameter of about 0.020 inches, and an axial length ofabout 90 cm. The pin plunger 148 comprises 0.014″ stainless wire, havinga length sufficiently longer than the needle tubing 218 to enable distaldeployment of the probe retention pin. Further construction details ofthe delivery catheter 138 will be apparent to those of skill in the artin view of the disclosure herein.

Referring to FIGS. 16-21A, further details of the docking structure 142and distal end 140 will become apparent from the discussion of themethod of using the delivery catheter 138.

Referring to FIG. 16, the delivery catheter 138 is illustrated inposition against the surface of a tissue structure 224, such as the wallof the esophagus. The distal end 214 of the intermediate tube 210 ispositioned within a lumen 130 which extends from a proximal end of theprobe 18 into the cavity 124. A blind end 132 is also in communicationwith the cavity 124 as has been discussed. At least one lockingstructure 226 such as a clip is provided in or near the blind end 132,for retaining the pin as will be discussed.

The probe 18 is releasably retained within the docking structure 142during the positioning step. Docking structure 142 comprises a body 228having a concavity 230 thereon for receiving the probe 18. A distalengagement structure 232 such as a proximally extending pin 234 isprovided on the docking structure 142, within the cavity 230. Engagementstructure 232 may comprise any of a variety of mechanical interfitstructures, adapted to cooperate with the distal end 214 of intermediatetube 210 to releasably retain the probe 18 within the cavity 230. In theillustrated embodiment, retention pin 234 extends proximally into arecess 236 on the distal end of the probe 18. One or more guide pins orother guide structures 238 may also be provided, as desired, to retainthe probe 18 in the proper position within cavity 230.

FIG. 16 illustrates the delivery catheter 138 in a position such thatthe probe 18 is in contact with the wall of the tissue structure 224.Vacuum has been applied to vacuum port 215, which is in communicationwith the cavity 124 by way of intermediate tube 210 and lumen 130. Inthis manner, a portion 240 of tissue 224 has been drawn within cavity124.

Referring to FIG. 17, the needle tubing 218 has been advanced distallywithin the intermediate tube 210, to advance the distal end 242 of aneedle 244 through the tissue portion 240. Needle 244 may comprise asharpened distal portion of the needle tubing 218, or may comprise aseparate needle tip which is secured to the distal end of the needletubing 218.

Referring to FIG. 18, the pin plunger 148 is thereafter advanceddistally the needle tubing 218 to advance a pin 246 distally out of thedistal end 242 of needle 244. The pin 246 is provided with acomplementary surface structure for engaging lock 226. Any of a varietyof mechanical interfit locking structures may be utilized, such as anannular recess on the outside surface of pin 246, which engages radiallyinwardly projecting tabs or flanges in the blind end 132. Alternatively,any of a variety of ramped or ratchet-type interference fit structuresmay be utilized. The pin has art axial length within the range of fromabout 3 mm to about 10 mm, and a diameter within the range of from about0.5 mm to about 2 mm. Any of a variety of materials, such as stainlesssteel, Nitinol or biocompatible polymers may be used for pin 246.

Following deployment of the pin 246, the needle tubing 218 and pinplunger 148 are proximally retracted to leave the pin 246 in position.Vacuum is disconnected and the intermediate tube 210 is proximallyretracted from lumen 130 to disengage the probe 18 from the dockingstructure 142. The delivery catheter 138 may be advanced slightlydistally to disengage the retention pin 234, or other removable lockingstructure, and the delivery catheter 138 is thereafter removed from thepatient leaving the probe 18 in position as shown in FIG. 21A.

Referring to FIG. 21, there is illustrated an alternate embodiment ofthe delivery catheter 138 at the procedural stage previously illustratedin FIG. 18. In the embodiment. of FIG. 21, an elongate flexible distalnose portion 250 is provided on the distal end 140 of the deliverycatheter 138. The distal nose 250 comprises a blunt, atraumatic tip,which enables deflection of the docking structure 142 along the softpalette during a transnasal approach. Nose 250 may comprise any of avariety of soft, flexible materials, such as silicone, neoprene, latex,and urethane.

A further embodiment of a delivery catheter 138 is illustrated in FIG.22A. Details of the distal end 140 including the docking structure 142are illustrated in FIGS. 22B-22E, which show sequential steps in thedeployment of a probe 18.

Delivery catheter 138 illustrated in FIG. 22A is provided with a control400 on the proximal end 200. Control 400 in the illustrated embodimentcomprises a housing 402 and a plunger or other manipulator 404. One ormore additional controls may be provided, depending upon the desiredfunctionality of the delivery catheter 138. In the illustratedembodiment, distal advancement of the plunger 404 enables deployment ofthe pin 246 as has been discussed. Proximal retraction of the plunger404, or manipulation of other component on control 400 proximallyretracts a locking wire 408 to release the probe 18 from the dockingstructure 142.

In this embodiment, the docking structure 142 is provided with a dockingsurface on concavity 234 for removably receiving the probe 18. The probe18 is retained on the docking structure 142 by a lock 406. In theillustrated embodiment, the lock 406 comprises a locking lumen 410 onthe probe 18, which, when the probe 18 is positioned on the dockingstructure 142, aligns with a lumen 412 which removably carries a lockingwire 408. See FIG. 22E. As will be seen by reference to FIGS. 22Bthrough 22E, proximal retraction of the locking wire 408 followingattachment of the probe 18 to the tissue 224 causes the locking lumen410 and probe 18 to become disengaged from the docking structure 142.

In addition to measuring pH in the esophagus, the probe 18 may beutilized to measure any of a variety of additional parameters such asesophageal pressure, and a respiratory rate. The probe 18 may also beutilized in the uterus to provide continuous or periodic monitoring oftemperature, as a fertility monitor. In a further embodiment, the probe18 may be utilized in the bladder to measure muscular contraction orpressure waves.

The deployment of the probe 18 may be accomplished under endoscopicvisualization as has been discussed. Alternatively, the probe 18 may beintroduced “blind” either through the mouth or through the nose.Confirmation that the probe 18 is in an appropriate position forattachment to the esophageal wall in a blind approach may beaccomplished by providing a pressure gauge in communication with thecavity 124. Occlusion of the cavity 124 will be observed on the pressuregauge, and provides an indication that tissue has been drawn into thecavity, so that deployment is appropriate.

Alternatively, the monitor 18 may be secured to the wall of theesophagus or other tissue surface by one or more bands which wrap aroundthe monitor 18 and are attached at either end to the tissue surface.Either end of the band may be attached to the tissue surface such asthrough the use of barbs or hooks, as discussed above. As a furtheralternative, the monitor 18 may be secured to the tissue surface using abioabsorbable suture as are known in the art. The suture may be passedthrough the mucosa, travel laterally through the submucosa and exit themucosa to form an attachment loop. The suture may travel over themonitor 18 and again travel through the mucosa, along the submucosa andexit the mucosa where it is. tied off with the other suture end. Thismay be accomplished using any of a variety of endoscopic instrumentsadapted for suturing as will be apparent to those of skill in the art.

In some embodiments, a computer software program is used to analyze thephysiological parameter data obtained over a period of time. Suchanalysis can include graphical representation of the data,identification of abnormal values outside the range of normal (such aspH values outside the range of about 4 to 7, which may represent refluxevents), and averaging of data values, among other types of analysisthat will be apparent to those skilled in the art.

The method of the present invention may comprise deploying two or threeor four or more probes in a single patient, to accomplish any of avariety of objectives. For example, multiple pH probes may be positionedat different axial distances along the wall of the esophagus from theLES, to monitor the change in pH as a function of distance from the LES.Each probe preferably transmits at a unique frequency or with a uniquecode to enable interpretation of the received data. In this aspect ofthe invention, each of the multiple probes monitors the same parameteror parameters. In an alternate aspect of the invention, two or moreprobes may be deployed within a patient such that each probe monitors atleast one analyte or parameter that is not monitored by the other probe.Thus, a first probe is positioned at a first site in the body, anddetects at least a first parameter. A second probe is positioned at asecond site in the body, and measures at least a second parameter.Installation of multiple probes may be accomplished utilizing proceduresand devices described above in connection with the installation of asingle probe. Data from each of the plurality of probes is preferablytransmitted and received in a manner which permits the received data tobe attributed to a particular

Probe. This may be accomplished, for example, by transmitting atdifferent RF frequencies, encoding the data, or any of a variety ofother manners which are well understood in the radio frequencytransmission arts.

FIG. 23 illustrates a circuit diagram of a preferred implementation of aphysiological parameter monitor circuit 300. The monitor circuit 300 iscontained within the monitor 18 and comprises circuitry to monitor pH,amplify and process the pH measurement, encode a digital message withinformation including the pH measurement, and transmit the digitalmessage via an RF transmitter 112 in a manner that will be described ingreater detail below.

The monitor circuit 300 comprises a power source 114 and a hermeticswitch 304. The power source 114 in this embodiment comprises two 5 mmsilver oxide coin cells connected in series and a plurality ofcapacitors that stabilize the output voltage. The hermetic switch 304 isa normally closed, magnetically activated switch. A permanent magnet isplaced adjacent the hermetic switch 304 in the shipping packaging of themonitor 18 to open the hermetic switch 304 and disconnect the powersource 114 from a microprocessor 116 and non-volatile memory 302. Whilethe monitor 18 is adjacent the permanent magnet in the shippingpackaging, the open hermetic switch 304 limits parasitic current drainthrough the microprocessor 116 and the non-volatile memory 302. When themonitor 18 is removed from the shipping packaging and distanced from thepermanent magnet included therein, the open hermetic switch 304 returnsto its normally closed position and permits current flow to the monitorcircuit 300.

The monitor circuit 300 also comprises a microprocessor 116, also calleda central processing unit (CPU). This microprocessor 116 can perform oneor more functions, including temporary storage or memory of data,reception of input signals from the transducer, comparison andcorrection of a signal with respect to a stored or measured referencesignal, and transformation between analog and digital signals, amongother functions that will be apparent to those skilled in the art.Moreover, in this embodiment, the microprocessor 116 includes aninternal clock for tracking a measurement/transmission cycle as will bedescribed in greater detail below. The microprocessor of this embodimentis a type 12C672 available from MicroChip, Inc. of Arizona.

The monitor circuit 300 also comprises non-volatile memory 302. Thenon-volatile memory is connected to and accessible by the microprocessor116. The non-volatile memory 302 stores calibration information for thetransducer 110. The non-volatile memory 302 also stores the uniqueidentification number for the monitor 18. The non-volatile memory 302will allow temporary storage of data accumulated over time (e.g., over aperiod of 24 hours for a typical gastroesophageal reflux study). Thenon-volatile memory is a type 24LC00 available from MicroChip, Inc. ofArizona.

The monitor circuit 300 also comprises a transducer 110. In thisembodiment the transducer 110 is configured to function as a pH sensor.In one embodiment, the transducer 110 comprises an ion sensitive fieldeffect transistor (herein after ISFET) 314. The ISFET 314 is a fieldeffect transistor that is responsive to ambient ion concentration, inthis embodiment, H+ ions. The ISFET 314 is switchably driven at aconstant voltage by the power source 114. The concentration of H+ ions,thereby the pH, in the fluid surrounding the ISFET 314 alters thecurrent flow through the ISFET 314. The current flows through a signalresistor 312 to ground and thus generates an initial pH signal acrossthis signal resistor 312. This initial pH signal is of very lowamplitude and is amplified by an amplification circuit 308 before beingsent to the microprocessor 116.

The non-inverting input of the amplification circuit 308 is driventhrough a voltage divider by the microprocessor 116. The pH signalgenerated by the ISFET 314 across the signal resistor 312 is connectedto the inverting input of the amplification circuit 308. The amplifiedpH signal is sent to the microprocessor 116. The amplified pH signaloutput from the amplification circuit 308 is also tied to a pH reference328. The pH reference 328 is a saturated potassium chloride gel that iswell known to those skilled in the art. In an alternative embodiment thepH reference 328 can comprise a silver/silver chloride solid statereference.

Hence, the pH level applied to the gate of the ISFET 314 results in avoltage appearing at the resistor 312 that is amplified and combinedwith the pH reference 328 signal before being sent to the microprocessor116. As the pH level changes, the voltage at the resistor 312 will alsochange as will the voltage being sent to the microprocessor 116. In thisway, the microprocessor 116 receives a signal that is indicative of thesensed pH level.

The monitor circuit 300 also comprises a transmitter 112. Thetransmitter 112 receives digital signals from the microprocessor 116 andtransmits the signals at a MHz frequency using an amplitude shift keyingtransmission format in a manner well known to those skilled in the art.The transmitter 112 comprises a RC filter network 316, an oscillator306, a transistor 318, RF coils 322, biasing network 324, and an antenna326. The microprocessor 116 sends a serial digital signal that will bedescribed in greater detail below on the GP2 pin through the RC filternetwork 316. The digital signal is superimposed on the MHz output of theoscillator 306. The combined signal triggers the base of the transistor318. The transistor 318 is connected to the biasing network 324 and alsoto the power source 114 through the RF coils 322. The RF coils 322comprise two inductors connected in series. The connection of the twoinductors is also connected to a first end of the antenna 326. Thetime-varying signal triggering the base of the transistor 318 generatesa corresponding time varying current in the RF coils 322 which induces atime varying field that is broadcast via the connected antenna 326.

In an alternative embodiment, the transducer 110 comprises an antimonyelectrode 350 as shown in FIG. 24. The antimony electrode 350 is adevice adapted to measure pH in a manner well known in the art. Themonitor circuit 300 of this embodiment is substantially similar to themonitor circuit 300 previously described wherein the transducer 110comprises the ISFET 314 and signal resistor 312. The antimony electrode350 and the pH reference 328 are connected to the amplification

circuit 308 in a manner well known in the art. The amplification circuit308 of this embodiment is adapted to provide approximately two to fivetimes signal amplification.

FIG. 25 shows a flow chart depicting the manner in which themicroprocessor 116 controls the operation of the monitor circuit 300.The microprocessor 116 and thereby the monitor circuit 300 has fivebasic operational states: non-active 348, measurement 336, correction338, message formation 340, and transmission 342. The microprocessor 116also has a calibration state 344 that is normally only performed onceprior to implanting the monitor 18 in a patient. The microprocessor 116performs three main decisions: is the monitor 18 calibrated 332, is ittime to make a measurement 334, and is a transmitter status messageneeded 346. The microprocessor 116 conducts a measurement cycle at avariable interval that in this embodiment is approximately every 6seconds. A transmission cycle is performed by the microprocessor 116every other measurement cycle, i.e. every 12 seconds in this embodiment.

The monitor circuit 300 initiates operation with a power on 330 statewhen the monitor 18 is removed from the shipping packaging and distancedfrom the permanent magnet included therein, which returns the openhermetic switch 304 to its normally closed position and permits currentflow to the monitor circuit 300. The microprocessor 116 then performsthe calibration decision 332. If the monitor 18 is calibrated themicroprocessor 116 performs the measurement decision 334. If themicroprocessor 116 determines that it is time to perform a pHmeasurement, the microprocessor places the monitor circuit 300 into themeasurement state 336.

The microprocessor 116 places the monitor circuit 300 into themeasurement state 336 by enabling the GP0 pin of the microprocessor 116which provides power to the transducer 110. The transducer 110 measuresthe pH, amplifies the signal, and sends the signal to the microprocessor116 in the manner already described. The measurement state 336 takesapproximately 20 ms. After the microprocessor 116 receives the pHmeasurement signal from the transducer 110, the microprocessor 116disables the transducer 110. By enabling the transducer 110 forapproximately 20 ms out of a 6second cycle, the monitor circuit 300realizes significant power savings compared to continuously monitoringthe pH and thus significantly extends the power source's 114 usefullife.

After the completion of the measurement state 336, the microprocessor116 enters the correction state 338. The microprocessor 116 calls thenon-volatile memory 302 for the calibration values stored therein. Themicroprocessor 116 then corrects the measured pH signal as needed in amanner well known to those skilled in the art.

Once the microprocessor 116 has completed the correction state 338, themicroprocessor 116 enters the message formation state 340. In themessage formation state 340, the microprocessor 116 prepares a digitalmessage in a manner that will be described in greater detail below. Oncethe microprocessor 116 has completed the message formation state 340,the microprocessor 116 enters the transmission state 342. Themicroprocessor 116 sends the digital message to the transmitter 112 fortransmission in the manner previously described.

Once the monitor circuit 300 completes transmitting a digital message,the microprocessor 116 returns to the calibration decision 332 and themeasurement decision 334. The correction 338, message formation 340, andtransmission 342 states together take approximately 60 ms. Ameasurement/transmission cycle is performed approximately every 12seconds. Thus the monitor circuit 300 spends much of its operationaltime in a non-active state 348. The non-active state 348 refers to theperiod during which neither the transducer 110 nor the transmitter 112is active and the microprocessor 116 is in a waiting mode. Thenon-active state 348 occupies most of the 12 secondmeasurement/transmission cycle. During the non-active state 348, themonitor circuit 300 and the monitor 18 consume a minimum amount of powerfrom the power source 114. In this embodiment, the microprocessor 116 isprimarily only operating an internal clock to track themeasurement/transmission cycle.

While the microprocessor 116 is performing the measurement decision 334,if a measurement is not needed, the microprocessor 116 monitors whethera transmitter status message is needed in the transmitter status state346. If the microprocessor 116 determines that a transmitter statusmessage does need to be sent, the microprocessor 116 prepares a digitalmessage containing information about the monitor circuit 300 status in amanner that will be described in greater detail below. The monitorcircuit 300 then transmits the status message in the manner previouslydescribed.

In order to provide accurate pH measurements, the monitor circuit 300must first be calibrated. The calibration can be performed at themanufacturer prior to shipment of the monitor 18 or can be performed bythe user prior to implantation of the monitor 18 in the patient.Calibration involves comparing the pH value measured by the transducer110 to that of the pH reference 328 in solutions of known pH andgenerating correction values. Typically two solutions of known pH areselected and prepared in a manner well known to those skilled in theart.

In the calibration decision 332, the microprocessor 116 checks whetheror not the non-volatile memory 302 has calibration values and if it doesnot, the microprocessor 116 puts itself into calibration state 344. Amessage is sent to the transmitter 112 to indicate that the monitorcircuit 300 is ready for the first solution. The monitor 18 is thenplaced in the first solution and the monitor circuit 300 measures the pHand prepares a first pH correction value with respect to the pHreference 328. The monitor circuit 300 then sends a message that themonitor circuit 300 has finished calibrating the first solution and isready for the second solution. The monitor 18 is then typically washedand inserted into the second solution. The monitor circuit 300 measuresa second pH value and generates a second pH correction value withrespect to the pH reference 328. The monitor circuit 300 then evaluatesthe calibration values and determines if the calibration procedure wassuccessful. A message is then sent indicating that either thecalibration is complete and successful or that calibration errorsoccurred. Once the calibration procedure is successfully completed, thenon-volatile . memory 302 stores the calibration information from the pHcalibration measurements.

The monitor 18 can be calibrated at the factory before it is packagedfor delivery. By pre-calibrating a number of monitors 18 at the factory,each monitor 18 can be more accurately calibrated. The precalibratedmonitor 18 is available for immediate use and does not require the userto prepare solutions of known pH or to perform the calibration procedureprior to using the monitor 18. Precalibration provides added economy,greater convenience for the user, and quicker availability forimplantation in the patient.

The microprocessor 116 formats digital signals to be transmitted via thetransmitter 112. The microprocessor 116 prepares digital messages in theformat shown in FIG. 26 in a manner well known to those skilled in theart. The digital message begins with a preamble. The message thenincludes a header that includes a digital signal identifying the monitor18. This transmitter ID is stored in and recalled from the non-volatilememory 302. The header then provides a message ID. The message IDspecifies what kind of information is being provided in the digitalmessage. The message ID can indicate that the information provided isthe transmitter status, calibration data, or pH measurements. A variablelength payload is then included which provides the data specified by themessage ID. The digital message concludes with a checksum.

The payload provides the main data of the digital message and is of avariable length depending on what information is being provided. If thetransmitter status is being sent, the payload tells whether or not thetransmitter is calibrated and whether the power supply 114 voltage islow enough to cause imminent transmitter shut down. The payload alsoprovides information about the current watchdog reset count, the monitorcircuit's 300 current transmit count, and the current power supply 114voltage.

If the message is providing calibration status information, the payloadprovides information that the monitor circuit 300 is in calibration modeand one of the following states: user is to prepare Liquid 1, themonitor circuit 300 is calibrating Liquid 1, the monitor circuit 300 isfinished calibrating Liquid 1 and is ready for the user to prepareLiquid 2, the monitor circuit 300 is calibrating Liquid 2, the monitorcircuit 300 has finished calibrating Liquid 2 and has not detectedcalibration errors, or the monitor circuit 300 has detected calibrationerrors. The message also provides two calibration values.

If the message is providing pH measurement information, the messagegives the last measured pH value. The message also provides the secondto last measured pH value.

Once the microprocessor 116 has formatted the message, the message issent via the GP2 pin of the microprocessor 116 to the transmitter 112 ina serial format in the previously described manner. Once thetransmission of the message is complete, the transmitter 112 and thetransducer 110 are inactive for the remainder of themeasurement/transmission cycle. As previously mentioned, the measurementcycle takes approximately 20 ms. The correction, message formation, andtransmission cycles together take approximately 60 ms. Together acomplete measurement/transmission cycle takes approximately 80 ms. Themonitor circuit 300 is inactive for the remainder of themeasurement/transmission period of approximately 12 seconds.

It can be appreciated that by only activating the monitor circuit 300for approximately 80 ms out of a 12 second period, the monitor 18consumes appreciably less power than it would by continuous operationand is thereby able to extend the life of the power supply 114. Inaddition, by alternating the active status of the transmitter 112 andthe transducer 110 and having the one not active in an inactive state,the monitor circuit 300 is able to further reduce its power consumptionrate and increase the life span of the power supply 114.

Although the present invention has been described in terms of certainpreferred embodiments, other embodiments of the invention will becomeapparent to those of skill in the art in view of the disclosure herein.Accordingly, the scope of the present invention is not intended to belimited by the foregoing, but rather by reference to the attachedclaims.

What is claimed is:
 1. An implantable gastroesophageal reflux monitor,comprising: a streamlined and smooth outer shell, shaped to pass throughthe gastrointestinal tract and to be excreted in the stool withoutinjury to the gastrointestinal mucosa, the shell comprising: a securingstructure for securing the shell to the wall of the esophagus, such thata portion of the wall of the esophagus is secured within an attachmentcavity of the shell, comprising a pin or a clip configured to penetratethe mucosa of the esophagus; a pH sensor; a radiofrequency transmitterfor transmitting pH data sensed by the pH sensor; and a power source. 2.The monitor of claim 1, said shell comprising a microprocessorconfigured to periodically receive a signal from the pH sensor andinduce the radiofrequency transmitter to send a radiofrequency signalindicative of the pH measured by the pH sensor.
 3. The monitor of claim2, wherein the microprocessor is configured to periodically enable thepH sensor during a first interval of each measurement cycle to obtain apH signal and then disable the pH sensor during a second interval. 4.The monitor of claim 2, wherein the microprocessor is configured toenable the radiofrequency transmitter during the second interval anddisable the radiofrequency transmitter during periods of each cycleother than the second interval and disable the pH sensor during periodsof each cycle other than the first interval.
 5. The monitor of claim 1,wherein the shell comprises an auxiliary sensor to measure an auxiliaryphysiological parameter that is not a pH parameter.
 6. The monitor ofclaim 5, wherein the auxiliary physiological parameter is selected fromthe group consisting of: an ion concentration, a temperature, and apressure.
 7. The monitor of claim 1, wherein the shell comprises avacuum lumen for drawing tissue into the attachment cavity.
 8. Themonitor of claim 7, wherein the securing structure comprises a pinconfigured to be movable from a retracted position within the shell toan extended position which extends at least part way across theattachment cavity.
 9. The monitor of claim 1, wherein the securingstructure comprises a pin and the shell comprises a blind end to receivea distal end of the pin.
 10. The monitor of claim 9, wherein blind endcomprises a lock.
 11. A system comprising: a monitor comprising: astreamlined and smooth outer shell, shaped to pass through thegastrointestinal tract and to be excreted in the stool without injury tothe gastrointestinal mucosa, the shell comprising: a securing structurefor securing the shell to the wall of the esophagus, such that a portionof the wall of the esophagus is secured within an attachment cavity ofthe shell, comprising a pin or a clip configured to penetrate the mucosaof the esophagus; a pH sensor; a radiofrequency transmitter fortransmitting pH data sensed by the pH sensor; and a power source; and areceiver configured to be worn by the patient.
 12. The system of claim11, wherein the receiver comprises circuitry configured to sense aposition of the patient, and the receiver is configured to periodicallyrecord the position of the patient.
 13. The system of claim 11, whereinthe receiver is configured to monitor a change in pH as a function ofdistance from a lower esophageal sphincter.
 14. The system of claim 11,wherein the shell comprises an auxiliary sensor to measure an auxiliaryphysiological parameter that is not a pH parameter and wherein thereceiver is configured to receive a pH reading from the pH sensor and toadjust the pH reading based on the measured value of the physiologicalparameter.